In the modern traffic theater, it is often required to monitor and enforce traffic laws and regulations, and/or control access to restricted areas and localities. For example, monitoring vehicle's speed is of utmost importance for a safe traffic arena.
One common method for enforcing the law on highways and byways is to employ police officers who monitor traffic manually and issue citations to violators when appropriate. Police officers make use of certain electronic devices, such as a laser gun, to determine vehicles speed. Their task is often limited to enforcing speed limit and only seldom are they engaged in monitoring and enforcing other traffic laws, such as overtaking past a solid divide line, ignoring "stop" and "yield" signs, and crossing an intersection in red traffic light. Moreover, this manual method is usually employed only during daylight and is inherently ineffective due to human limitations. Many violators may escape while the officer is engaged in issuing one citation. Also, the presence of police may be detected by vehicle operators who momentarily obey the law.
Apart from enforcement by means of a close human intervention, there also exist certain semi-automatic systems, such as the one involving a camera that monitors vehicles crossing an intersection in red traffic lights. In this system a camera is activated by a magnetic sensor embedded inside the intersection. This sensor is sensitive to the presence of large metallic masses, but can not be relied upon for determining the exact position of the metallic mass. The still photographs thus acquired by the camera are stored internally for periods of days or weeks, until they are retrieved and examined manually.
Other devices include a rubber coated cable housing a piezoelectric detector along its length. This type of road sensor is commonly used in counting the number of vehicles traveling on the road. By its very construction, this sensor has a short life span, is prone to tempering by unauthorized individuals, and is inaccurate in determining time of event at a given point on the road since it tends to be dragged by the impacting wheel. Another existing road sensor is known as the magnetic loop. Here, changes in a current flowing in a conductor in the form of a loop that is caused by inductance are recorded and interpreted as indicating the approach of a metal body. This sensor is adequate for detection of a moving vehicle, but is inadequate for a precise measurement of location and time since the induced current is highly sensitive to the mass of the moving target. Moreover, it is very sensitive to electromagnetic radiation, such as that present near power lines.
Other passive sensors for detecting motion include an electronic setup involving a photoelectric cell, as the one mentioned above. This detector would be triggered by a passing body that causes a discontinuity in the collimated light signal, much like the systems employed by automatic doors. However, such detector that is not housed inside a robust enclosure, as in the present invention, will be unreliable, prone to weather hazards such as rain, wind, and dust, and also prone to tempering by vandals.
Other existing road sensors are of the active type and include laser and radar detectors. These sensors, again, are placed on the surface and may not be enclosed inside a protecting enclosure. Moreover, these sensors are imprecise and limited in their functionality to determining the speed of a passing vehicle, and usually require a human operator for recording the events.
To summarize, the situation on the highways everywhere in the developed world is grave and becoming even more so with the natural increase in standards of living. The current statistics for the state of Israel includes a traffic accident every 25 min, a fatal accident every 18.5 hrs, a pedestrian involved in an accident every 2 hrs, and human injury every 14 min. Clearly, the solution may be found in either a massive increase in law enforcement personnel, or by exploiting novel technological methods and means.